Enteric pathogens cause disease among individuals living in both developing and industrialized countries, with some pathogens being universal, while others are largely restricted to certain settings. Certain enteric pathogens are epidemiologically emerging or re-emerging. Travelers from industrialized countries who visit developing countries form a special risk group that bridges the two broad ecologies. Finally, a few enteric pathogens are of special interest from the civilian biodefense perspective, as they have been used by nefarious individuals to promulgate bioterror (non-typhoidal Salmonella), or have properties that suit them to such a purpose (Shigella dysenteriae 1). The five Projects described in this Enteric Center for Excellence in Translation Research (Enteric CETR) proposal, bonded by the theme Immunoprophylactic Strategy to Control Emerging Enteric Infections, will undertake translational research towards developing products to prevent enteric disease caused by several important bacterial and protozoal pathogens, including: the enteric fever Salmonella serovars S. Typhi, S. Paratyphi A and S. Paratyphi B (Project 1); Clostridium difficile (Project 2); Shigella, enterotoxigenic E. coli (ETEC), enteroaggregative E. coli (EAEC) and Shiga toxin-producing enterohemorrhagic E. coli (EHEC) diarrheal pathogens (Project 3); non-typhoidal Salmonella serovars that cause invasive disease and/or gastroenteritis (emphasizing group C serovars) (Project 4); the protozoan species Cryptosporidium hominis and C. parvum (Project 5). Whereas each pathogen represents an important public health priority, only one, S. Typhi, already has licensed vaccines to prevent disease and those are not ideal. Three projects intend to progress new vaccine candidates to the point where Investigational New Drug Applications (IND) could be prepared to initiate Phase 1 clinical trials. These include: i) a Shigella live vector vaccine expressing protective antigens to prevent clinical illness caused by several pathotypes of diarrhea-causing Escherichia coli (Project 3); ii) Core-O polysaccharide-flagellin conjugate parenteral vaccines, as well as engineered recombinant attenuated strains, to prevent invasive disease caused by non-typhoidal serovars of Salmonella Group C1 & C2 (Project 4); iii) a vaccine based on proteins from C. hominis and C. parvum sporozoites; iv) a bivalent adjuvanted cTxAB toxoid vaccine to prevent recurrent C. difficile disease (Project 2). We will also investigate a unique passive antibody approach to prevent C. difficile disease (Project 2). Finally, Project 1 aims to explain the cross protection observed in large-scale field trials wherein oral immunization with live S. Typhi vaccine strain Ty21a conferred cross protection against S. Paratyphi B, whereas no protection was afforded against S. Paratyphi A. Most projects will utilize innovative animal models including senescent mouse models (to explore how aging influences immune response to vaccines) and the gnotobiotic piglet model. All projects include collaborations of investigators across multiple institutions of he consortium. The Enteric CETR PL/PD is highly experienced in translational research and vaccine product development.